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We found that miR-20a, miR-17-5p, and miRNA106b affected signiﬁcantly luciferase expression (Fig. 1B). In contrast, a scrambled miRNA sequence, as well as the other candidate miRNAs (miR-15a, miR-130a, let-7d and let-7a) showed no effect in this assay. Curiously, miR-106a, which is closely related to miR-106b, had in this assay an inconsistent effect.
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Gene dosage effects of Amyloid precursor protein (APP) can cause familial AD. Recent evidence suggest that microRNA (miRNA) pathways, implicated in gene transcriptional control, could be involved in the development of sporadic Alzheimer's disease (AD). We therefore investigated whether miRNAs could participate in the regulation of APP gene expression. We show that miRNAs belonging to the miR-20a family (that is, miR-20a, miR-17-5p and miR-106b) could regulate APP expression in vitro and at the endogenous level in neuronal cell lines. A tight correlation between these miRNAs and APP was found during brain development and in differentiating neurons. We thus identify miRNAs as novel endogenous regulators of APP expression, suggesting that variations in miRNA expression could contribute to changes in APP expression in the brain during development and disease. This possibility is further corroborated by the observation that a statistically significant decrease in miR-106b expression was found in sporadic AD patients.